Polyurea polyrethanes having improved physical properties

ABSTRACT

A process for preparing oil and petroleum-resistant cellular to solid (polyurea)polyurethanes (PURS) with improved physical properties in which a polyether polyol component having a number average molecular weight of from 1000 to 8000 and a polyester polyol component having a number average molecular weight of from 1000 to 6000 are reacted with a polyisocyanate and the (polyurea) polyurethanes produced by that process. The (polyurea)polyurethanes are particularly useful for personal safety equipment and in the construction of automobiles.

BACKGROUND OF THE INVENTION

The invention provides a process for preparing oil and petrol-resistantcellular to solid (polyurea)polyurethanes (PURs) with improved physicalproperties, such as are required for personal safety equipment and forthe construction of automobiles.

The wide variety of polyurethane plastics, their structure and methodsof preparation has represented the prior art for many years. WO 98/23659describes polyetherpolyurethanes which are relatively petrol-resistant.However, these swell in an obvious manner on contact with hydrocarbonsand thus their mechanical and physical properties become modified. Inaddition, when processing polyetherpolyurethanes to produce mouldedarticles, the moulds become heavily soiled.

The polyester-PURs generally used hitherto in such applications have thefollowing disadvantages:

-   -   the high viscosity of the components when ready for processing        leads to problems with the accurate reproducibility of moulded        articles;    -   the temperatures of 40–60° C. required for processing reduces        the useful lifetime of the system components;    -   inadequate resistance to hydrolysis and microbes leads to a        limited operational lifetime for the products;    -   the ability to control the polyaddition reaction by catalysts is        restricted since these often promote glycolysis of the ester.

SUMMARY OF THE INVENTION

It has now been found that the addition of only 3 to 30 wt. %, based ontotal weight of polyether polyol component A1) and polyester polyolcomponent A2), of specific polyesterpolyols to knownpolyetherpolyurethanes greatly improves their resistance to swelling inoil and petrol.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph of the results of the sterile hydrolysis testconducted on specimens aged at 70° C. and 95% relative humidity for aperiod of 7–14 days.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides oil and petrol-resistant cellular to solid(polyurea)polyurethanes, obtainable by reacting a reaction mixturecomprising

-   -   A1) a polyetherpolyol component with a number average molecular        weight of 1000 to 8000 g/mol, preferably 2000 to 6000 g/mol,    -   A2) a polyesterpolyol component with a number average molecular        weight of 1000 to 6000 g/mol, preferably 1000 to 4000 g/mol,    -   B) a polyisocyanate component,    -   C) chain-extending agents,    -   optionally    -   D) blowing agents and    -   E) activators and other auxiliary substances and additives,        wherein the starting materials are reacted while maintaining the        isocyanate index at a value of 70 to 130.

Polyetherpolyol component A1) has a number average molecular weight of1000 to 8000 g/mol and has a hydroxyl functionality of 2.0 or issubstantially a mixture with an average hydroxyl functionality of 2.02to 2.95 composed of

-   -   a) at least one polyetherdiol with a hydroxyl value in the range        10 to 115, which has been prepared by propoxylation of a        difunctional starter and subsequent ethoxylation of the        propoxylation product while maintaining a ratio by weight of        propylene oxide to ethylene oxide of 60:40 to 85:15 and    -   b) at least one polyethertriol with a hydroxyl value in the        range 12 to 56, which has been prepared by propoxylation of a        trifunctional starter and subsequent ethoxylation of the        propoxylation product while maintaining a ratio by weight of        propylene oxide to ethylene oxide of 60:40 to 85:15 and which        optionally contains fillers based on styrene/acrylonitrile        copolymers, polyureas or polyhydrazocarbonamides in an amount of        up to 20 wt. %, with respect to the total weight of component        b).

Suitable compounds for use as component A2) are polyesterpolyols with anumber average molecular weight of 1000 to 6000 g/mol, which have beenprepared, for example, from organic dicarboxylic acids with 2 to 12carbon atoms, preferably aliphatic dicarboxylic acids with 4 to 6 carbonatoms and polyhydric alcohols, preferably diols, with 2 to 12 carbonatoms, preferably 2 carbon atoms. Suitable dicarboxylic acids are, forexample: succinic acid, glutaric acid, adipic acid, suberic acid,azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid,fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. Thedicarboxylic acids may be used individually or in a mixture with eachother. Instead of the free dicarboxylic acids, the correspondingdicarboxylic acid derivatives, such as e.g. the monoesters and/ordiesters of dicarboxylic acids with alcohols with 1 to 4 carbon atoms ordicarboxylic acid anhydrides, may be used. Dicarboxylic acid mixtures ofsuccinic, glutaric and adipic acids in the ratio of, for example, 20 to35 parts by wt. of succinic acid to 35 to 50 parts by wt. of glutaricacid to 20 to 32 parts by wt. of adipic acid are preferably used. Theuse of adipic acid is particularly preferred. Examples of dihydric andpolyhydric alcohols, in particular diols and alkylene glycols, are:ethanediol, diethylene glycol, 1,2- or 1,3-propanediol, dipropyleneglycol, methylpropane-1,3-diol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, neopentyl glycol, 1,10-decanediol, glycerol,trimethylolpropane and pentaerythritol. 1,2-ethanediol, diethyleneglycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane ormixtures of at least two of the diols mentioned are preferred, inparticular mixtures of ethanediol, diethylene glycol, 1,4-butanediol,isobutyl glycol, 1,3-propanediol, 1,2-propanediol, neopentyl glycol,1,6-hexanediol, glycerol and/or trimethylolpropane. Furthermore,polyesterpolyols formed from lactones, e.g. ε-caprolactone, orhydroxycarboxylic acids, e.g. o-hydroxycaproic acid and hydroxyaceticacid, may also be used.

To prepare the polyesterpolyols, the organic, e.g. aromatic andpreferably aliphatic polycarboxylic acids and/or derivatives of theseand polyhydric alcohols are polycondensed without the use of a catalystor in the presence of esterification catalysts, expediently in anatmosphere of inert gases, such as e.g. nitrogen, carbon monoxide,helium, argon, or also in the molten state at temperatures of 150 to300° C., preferably 180 to 230° C., optionally under reduced pressure,until the acid value required is reached, this being advantageously lessthan 10 and preferably less than 1.

According to a preferred embodiment, the esterification mixture ispolycondensed at the temperatures mentioned above until reaching an acidvalue of 80 to 30, preferably 40 to 30, under atmospheric pressure andthen under a pressure of less than 500 mbar, preferably 10 to 150 mbar.Suitable esterification catalysts are, for example, iron, cadmium,cobalt, lead, zinc, antimony, magnesium, titanium and tin catalysts inthe form of metal, metal oxides or metal salts. Polycondensation mayalso be performed in the liquid phase, however, in the presence ofdiluents and/or entraining agents such as e.g. benzene, toluene, xyleneor chlorobenzene, for azeotropic distillation of the condensation water.

To prepare the polyesterpolyols, the organic polycarboxylic acids and/orderivatives are advantageously polycondensed with polyhydric alcohols inthe ratio by moles of 1:1 to 1.8, preferably 1:1.05 to 1.2. Thepolyesterpolyols obtained preferably have a functionality of 2 to 3, inparticular 2 to 2.6 and a number average molecular weight of 400 to6000, preferably 800 to 3500.

Suitable polyesterpolyols are also polycarbonates which contain hydroxylgroups. Suitable polycarbonates which contain hydroxyl groups are thoseof a type known per se which can be prepared, for example, by reactingdiols such as 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol,diethylene glycol, trioxyethylene glycol and/or tetraoxyethylene glycolwith diaryl carbonates, e.g. diphenyl carbonate or phosgene.

Polyesterpolyols with the following composition (compounds from whichthe building blocks of repeating units in the polyol are derived arecited) are particularly suitable for preparing (polyurea)polyurethanesaccording to the invention:

adipic acid 20–50 mol. %, preferably 40–48 mol. % glutaric acid  0–20mol. %, preferably 0 mol. % succinic acid  0–10 mol. %, preferably 0mol. % neopentyl glycol 10–30 mol. %, preferably 19–23 mol. % hexanediol10–40 mol. %, preferably 30–35 mol. % ethanediol  0–15 mol. %,preferably 0–5 mol. % butanediol 10–20 mol. %, preferably 0–5 mol. %Polyesterpolyols with the following compositions are preferably used:

-   -   1. 47.1 mol. % adipic acid, 19.4 mol. % neopentyl glycol, 30.6        mol. % hexanediol, 2.9 mol. % butanediol;    -   2. 47.1 mol. % adipic acid, 19.4 mol. % neopentyl glycol, 30.6        mol. % hexanediol, 2.9 mol. % ethanediol;    -   3. 47.1 mol. % adipic acid, 19.4 mol. % neopentyl glycol, 30.1        mol. % hexanediol, 1.7 mol. % butanediol, 1.7 mol. % ethanediol.

Polyesterpolyols with this composition are miscible with thepolyetherpolyols described under A1) over wide limits and exhibit notendency to separate. In contrast to this, commercially availableethanediol/butane-1,4-diol/polyadipates (e.g. Bayflex® 2002H, Bayer AG)begin to separate out above a concentration of 5 wt. % in thepolyetherpolyols mentioned.

As a result of adding these polyesterpolyols, the physical andmechanical properties of the PURs are affected positively without thenegative properties of polyesterpolyols being detectable. The use ofthese esters which are compatible with polyetherpolyols enables targetedoptimisation of the properties of (polyurea)polyurethanes according tothe invention since polyol mixtures can be used which contain between 0and 100% of ethers and correspondingly between 100 and 0% of esters,preferably 70 to 95 wt. % of ethers and 5 to 30 wt. % of esters. Anotheradvantage is that transparent materials can be prepared with these typesof polyol mixtures in any of these compositions.

Compounds for use as component B) are industrially readily accessiblepolyisocyanates such as diisocyanatodiphenylmethane, toluenediisocyanate and mixtures of these with partially carbodiimidisedisocyanates in pre-extended form with an NCO content of 5 to 30 wt. %.Polyethers or polyesters or mixtures with the structure described undercomponents A1) and A2) which have a hydroxyl functionality of 2 to 2.5are used for pre-extension purposes.

Compounds for use as component C) are ethanediol, diethylene glycol,butanediol, methylpropanediol, propylene glycol, triethanolamine,glycerol, diaminoethyltoluylene or mixtures of these compounds.Compounds for use as component D) are optionally water and/or a physicalblowing agent, e.g. R 134a (a mixture of hydrofluoroalkanes).

Catalysts and optionally incorporated auxiliary substances and additivesE) which may be used are activators such as e.g. tertiary amines, tin ortitanium compounds and, depending on the requirements, surface activesubstances, foam stabilisers, cell regulators, internal mould releaseagents, colorants, pigments, anti-hydrolysis agents, substances whichprevent the growth of fungi and bacteria, oxidising agents, lightprotection agents and antistatic agents, which are disclosed in theliterature.

(Polyurea)polyurethanes according to the invention are prepared bymethods known in principle by a person skilled in the art. In general,components A) and C) to E) are combined with a polyol component andreacted in a one-stage reaction with isocyanate component B), whereinconventional two-component mixing units may be used. Component A2) maybe a constituent of both the polyol component and the isocyanatecomponent.

The grades of PUR obtained are suitable in particular for preparingsoles of shoes which comply with safety shoe standard EN 344, but mayalso be used for wheels, rollers, flexible tubing and tires due to theirability to withstand a high degree of stress.

EXAMPLES 1–6

Starting Materials

Polyhydroxyl Compounds A

-   -   A1: Propylene oxide/ethylene oxide random block polyether        started with trimethylolpropane and propylene glycol; OH value        28; functionality 2.1;    -   A2a: Ethanediol/butane-1,4-diol/polyadipate; OH value 56;        functionality 2;    -   A2b: Polyersterpolyol containing 47.1 mol. % of units derived        from adipic acid, 19.4 mol. % of units derived from neopentyl        glycol, 30.6 mol. % of units derived from hexanediol and 2.9        mol. % of units derived from butanediol;        Polyisocyanate B    -   B: Soft segment pre-polymer with a number average molecular        weight of 4000, the reaction product of MDI with TPG and a PO/EO        random block polyetherdiol, NCO value: 17 wt. %;        Chain-Extending Agent C

Butanediol;

Catalyst E

Mixture of diazabicyclooctane (DABCO) and dibutyltin dilaurate (DBTDL)in a ratio of about 96:4.

Method Used

Components A1, A2 and C were mixed in accordance with the data in table1 and reacted with isocyanates B1 or B2 in a conventional two-componentmixing and metering unit by the low pressure method and introduced intoan aluminium mould, the surface of which had not been treated in any waynor provided with external mould release agents. After a reaction timeof 2.5 to 4 minutes, the moulded item was removed. The mechanicalproperties were determined 48 hours after producing test plates(200×200×10 mm³), from which conventional test specimens were preparedand measured as described in the standards (DIN 53504 S1 rod, DIN 53507tear propagation resistance, abrasion DIN 53516; oil and petrolresistance DIN EN 344). The results are summarised in table 1.

TABLE 1 Example 1* 2 3 4 5 6 A1 [wt. %] 91.3 81.27 81.27 71.27 61.2747.18 A2a [wt. %] — 10.0 — — — — A2b [wt. %] — — 10.0 20.0 30.0 40.0 C[wt. %] 8.0 8.0 8.0 8.0 8.0 12.0 E [wt. %] 0.73 0.73 0.73 0.73 0.73 0.52D: water — — — — — 0.3 [wt. %] Phase-stable yes no yes yes yes yes B[wt. %] 55 55 55 54 53 89 Bulk density 950 950 950 950 950 600 [kg/m³]Hardness 60 60 60 60 60 55 [Shore A] Tensile 9.5 10.0 9.9 11.5 9.1 5.4strength [MPas] Elongation at 660 630 640 610 550 520 break [%] Tear13.5 12.0 13.2 12.9 12.2 6.5 propagation resist. [kN/m] Abrasion [mg]150 140 130 120 105 180 Volume change 11 10 9 6 3.5 11 in isooctane [%]*Comparison example, not in accordance with the invention

Whereas with conventional ester formulations, the moulds have to becleansed weekly, when processing polyether formulations it isconventional to cleanse the moulds daily. With the new hybridformulations, about 800 mould release operations can be performedwithout any detectable build-up in the moulds, which correspondsapproximately to a cleansing cycle of 4 days.

In a test where articles were buried in soil under defined conditions(30° C., 95% rel. humidity, in humus soil enriched with moulds, for 8weeks), it can be shown that addition of the ester does not impair thelong-term resistance to microbial degradation. Pure esterpolyurethaneshave obvious cracks in the surface of the material after four weeksunder these conditions. Similar positive results were obtained in asterile hydrolysis test in which the specimens were aged at 70° C., 95%rel. humidity for a period of 7 to 14 days (FIG. 1).

In trials with various shapes of moulds for soles, a decrease in thefrequency of bubbles in the frame region of the sole was observed whenpure polyether formulations were replaced by higher viscosityether/ester formulations.

1. A process for the production of a (polyurea)polyurethane which is oiland petroleum resistant as determined in accordance with DIN EN 344comprising reacting a mixture comprising A1) a polyether polyolcomponent having a number average molecular weight of from 1000 to 8000g/mol and a hydroxyl functionality of 2.0 or is substantially a mixturewith an average hydroxyl functionality of 2.02 to 2.95 comprising a) atleast one polyether diol with a hydroxyl value in the range of 10 to 115prepared by propoxylation of a difunctional starter compound andsubsequent ethoxylation at a ratio by weight of propylene oxide toethylene oxide of 60:40 to 85:15 and b) at least one polyether triolwith a hydroxyl value in the range of 12 to 56 prepared by propoxylationof a trifunctional starter compound and subsequent ethoxylation at aratio by weight of propylene oxide to ethylene oxide of 60:40 to 85:15,A2) from 3 to 30 wt. %, based on total weight of components A1) and A2),of a polyester polyol component having a number average molecular weightof from 1000 to 6000 g/mol prepared by polycondensation of a) an organicpolycarboxylic acid and/or a derivative thereof and b) a polyhydricalcohol, B) a polyisocyanate component, C) a chain extending agent, andoptionally, D) a blowing agent and/or E) an additive at an isocyanateindex of from 70 to
 130. 2. The process of claim 1 in which thepolyester polyol component comprises (1) from 20 to 50 mol %, based onmols of polyester polyol, of units derived from adipic acid, (2) from0–20 mol %, based on mols of polyester polyol, of units derived fromglutaric acid, (3) from 0 to 10 mol %, based on mols of polyesterpolyol, of units derived from succinic acid, (4) from 10 to 30 mol %,based on mols of polyester polyol, of units derived neopentyl glycol,(5) from 10–40 mol %, based on mols of polyester polyol, of unitsderived from hexanediol, (6) from 0–15 mol %, based on mols of polyesterpolyol, of units derived from ethanediol, and (7) from 10–20 mol %,based on mols of polyester polyol, of units derived from butanediol,with the sum of (1) through (7) totalling 100 mol %.
 3. The process ofclaim 2 in which the polyester polyol component is included in thepolyisocyanate component.
 4. The process of claim 1 in which thepolyester polyol component is included in the polyisocyanate component.5. The process of claim 1 in which the polyether polyol component,polyester polyol component, chain extending agent, any blowing agent andany additive are combined before being reacted with the polyisocyanatecomponent.
 6. The oil and petroleum-resistant (polyurea)polyurethaneproduced by the process of claim
 2. 7. The oil and petroleum-resistant(polyurea)polyurethane produced by the process of claim
 1. 8. The(polyurea)polyurethane of claim 7 which is transparent.
 9. The(polyurea)polyurethane of claim 7 which is resistant to hydrolysis andmicrobial action.
 10. A shoe sole composed of the (polyurea)polyurethaneof claim
 7. 11. Safety clothing produced from the (polyurea)polyurethaneof claim
 7. 12. Flexible tubing produced from the (polyurea)polyurethaneof claim 7.